Question

我有以下问题：我的目标是一次获得两行。它的两倍相同＆＃34;选择＆＃34;声明，只是另一个ID。用我的代码我得到第二行。如何同时获得两条线？

select 
table1.attr1 + table2.attr2 as total,
table1.id
FROM  table1, table2
WHERE table.id = 1 AND table2.id = 1;

select 
table1.attr1 + table2.attr2 as total,
table1.id
FROM  table1, table2
WHERE  table.id = 2 AND table2.id = 2;

Answer 1

将明确的joins与on子句一起使用：

select t1.attr1 + t2.attr2 as total
     , t1.id
FROM  table1 t1 join table2 t2 on t1.id = t2.id
WHERE t1.id in (1, 2)

Answer 2

修改您的加入条件：

SELECT
    table1.attr1 + table2.attr2 as total,
    table1.id
FROM  table1, table2
WHERE (table.id = 1 AND table2.id = 1)
    OR (table.id = 2 AND table2.id = 2)

首先选择一行，然后选择第二行

2 个答案: